Lung cancer is a global scourge responsible for 1.4 million deaths worldwide and ~160,000 deaths in the USA this year alone. Despite the grim clinical picture, cancer genetics has revealed that lung cancers can be divided into genetically-defined subsets based on driver oncogene mutations that, in turn, serve as predictive biomarkers for the clinical deployment of new first-line pathway-targeted therapies in lung cancer patients. However, to date, only a minority of such patients have benefitted from these advances such that treatment options for most patients remain poor and are limited to conventional approaches including surgery, radiation, and/or conventional chemotherapy that are ineffective against tumor cells and toxic to normal cells. The overarching, long-term goal of this research is to aid the deployment of rational, evidence-based therapeutic strategies to treat lung cancer patients. However, the immediate objectives of this proposal are to mechanistically define how parallel pathways, such as WNT?-catenin?c-MYC or PI3'-kinase?PDK?AKT signaling, cooperate with oncogenic KRASG12D or BRAFV600E in the genesis and maintenance of lung cancer. To do so we will use: State-of-the-art genetically engineered mouse models of lung cancer; Lung cancer- derived cell lines whose aberrant behavior is driven by relevant genetic abnormalities; Pathway-targeted therapeutics, many of which are in cancer clinical trials and one of which is specifically being tested in lung cancer and; An innovative transposon mutagenesis system to simultaneously elicit lung cancer progression and identify its underlying genetic cause. Building on a solid foundation of studies published in the previous cycle of this grant, in Aim 1 we will identify the tumor cell autonomous mechanisms by which WNT?-catenin signaling cooperates with oncogenic KRASG12D or BRAFV600E in the genesis and maintenance of lung cancer. In Aim 2 we will explore the mechanisms by which PI3'-kinase signaling promotes the proliferative expansion and maintenance of both early- and late-stage BRAFV600E-induced lung tumors. BRAFV600E-induced lung tumors remain uniformly benign unless cooperating genomic events unleash malignant progression. In Aim 3 document the use of Sleeping Beauty (SB) transposon mutagenesis to promote progression of BRAFV600E- driven lung cancers. Genetic progression factors identified will be validated using lentivirus-mediated cDNA expression or by in vivo CRISPR/Cas9-mediated tumor suppressor gene silencing in the mouse lung. Moreover, we will mine the TCGA lung adenocarcinoma genome, RNA sequencing and RPPA databases to credential genes implicated in our SB screen in mice as being directly relevant to bona fide human lung cancer. Finally, although this proposal is focused primarily on studies of genetic cooperation in the genesis of lung cancer, we will test the anti-tumor effects of novel pathway-targeted inhibitors of BRAFV600E, WNT or PI3'- kinase signaling that are likely to have important translational implications for the design and evaluation of new pathway-targeted strategies to treat patients with this ubiquitous, devastating and poorly understood disease.